The background of the invention will be discussed in two parts:
1. Field of the Invention
This invention relates to frequency scanned radar antennae, and more particularly to a radar antenna having a scan back system which provides for more dwell time on the target.
2. Description of the Prior Art
In radar scanning systems, some such systems employ antennae that are mechanically rotated in azimuth and frequency-scanned in elevation to provide three-dimensional aircraft or target object position data. The antennae in such systems employ a number of spaced radiating elements, preferably in a fixed array, with some form of delay means in the line feeding the radiating element. For frequency scanning, a wave front is generated by the radiating elements in a given direction, that is, at a pointing angle, with the wave front corresponding to a line in a space along which the signals emanating from the radiating elements are in phase with one another. The phase coincidence from one element to another is controlled by the interconnecting delay means, such as a tapped delay line, or slow wave structure, that may be folded, helically wound, or dielectrically loaded in form. The folded form is called a serpentine.
In such systems, volumetric aerial coverage may be obtained by radiating an orderly progression of sequentially generated transmitter signals, each at a different RF frequency as the antenna rotates. In such systems, the dwell time on target is a direct function of the speed of rotation of the antenna and the beam pattern, in both planes, of the radiating elements of the antenna. For low flying, line of sight, high speed targets, some difficulty is encountered, primarily due to the pencil beams used in such systems, coupled with the rate of scanning.
It is accordingly an object of the present invention to provide a new and improved radar system.
It is another object of the present invention to provide a new and improved radar system with provision for scan back, forward or both from an auxiliary antenna for enabling more dwell time on target.
It is still another object of the present invention to provide a new and improved antenna system using an auxiliary space fed array antenna with diode phase shifters to provide more dwell time on target.
It is a further object of the present invention to provide a new and improved antenna system utilizing a counter-rotating multi-sided prism to provide more dwell time on target.